The present invention relates to a fixing device and an image forming apparatus having the fixing device.
In an image forming apparatus such as a printer, a copier, a facsimile, and an MFP (Multifunction Peripheral), an image is formed on a recording medium through the following process. First, a charge roller charges a surface of a photosensitive drum. An exposure device such as an LED (light emitting diode) head exposes the surface of the photosensitive drum to form a static latent image or a latent image thereon. A developing roller attaches a thin layer of toner to the static latent image to form a toner image. A transfer roller transfers the toner image to the recording medium. A fixing unit or fixing device fixes the toner image to the recording medium before the recording medium is discharged outside the fixing device.
In the fixing device, a pressing roller is pressed against a fixing roller to form a nip portion therebetween. When the recording medium passes through the nip portion after the toner image is transferred thereto, the toner image is heated and pressed, thereby fixing the toner image to the recording medium. The fixing roller and the pressing roller are coated with a fluorine resin layer, so that toner is not easily stick thereto. Accordingly, when the recording medium passes through the nip portion, the recording medium tends to be statically charged through friction.
When the recording medium is discharged from the fixing device in a charged state, it is difficult to properly transport the recording medium due to the static charge on the recording medium. To this end, there has been proposed a fixing device having a discharging brush as a discharging member for discharging a recording medium (refer to Patent Reference). The discharging brush is arranged to contact with the recording medium when the recording medium passes through the nip portion.
In the conventional fixing device disclosed in Patent Reference, there is disclosed no specific attaching member for attaching the discharging brush to the fixing device. Instead of a specific attaching member, the discharging brush is attached to a brush supporting member with one side of a conductive double-sided adhesive tape, and is attached to a metal plate frame with the other side of the conductive double-sided adhesive tape. The metal plate frame is grounded and supports the fixing roller and the pressing roller. The discharging brush contacts with a surface of the recording medium, thereby removing electric charges on the surface of the recording medium.
Patent Reference Japanese Patent Publication No. 2002-91217
In the conventional fixing device, the metal plate frame has high heat conductivity. Accordingly, the metal plate frame easily receives heat from the fixing device, and tends to become very hot during an operation of the fixing device. As a result, a temperature of the conductive double-sided adhesive tape attaching the discharging brush increases, so that the conductive double-sided adhesive tape may come off. Consequently, it is difficult to properly contact the discharging brush with the metal plate frame, thereby making it difficult to stably discharge the recording medium with the discharging brush.
In view of the problems described above, an object of the present invention is to provide a fixing device and an image forming apparatus capable of solving the problems of the conventional fixing device. In the fixing device, a discharging member is sandwiched and held between a frame member and a cover member. The frame member supports a fixing member and a pressing member, and the cover member covers the frame member. Accordingly, it is possible to securely ground the discharging member without causing poor electric conductivity, thereby making it possible to stably discharge a recording medium and transport the recording medium.
Further objects and advantages of the invention will be apparent from the following description of the invention.